Answer this question truthfully
### Question: When does an inhaler need to be replaced?
### Response: A metered dose inhaler contains enough medication for a certain number of puffs which is printed on the canister. Even though the inhaler may continue to work beyond that number of uses, the amount of medication delivered may not be correct. It is important to keep track of the number of times an inhaler was used, so that it can be replaced after its recommended number of uses. The manufacturer of Ventolin has addressed this issue by adding in a counter to the mouthpiece, as has the manufacturer of Advair. Also, depending on the manufacturer, inhalers are sold as a complete unit or the individual canister as a refill prescription.